Manufacture of snap-acting devices



Dec. 29, 1964 H. D. EPSTEIN MANUFACTURE OF SNAP-ACTING DEVICES Filed Aug. 25, 1961 FIG.3.

United States Patent 3,163,140 MANEJEACTURE (BF SNAP-AQTING DEVIQES Henry David Epstein, Cambridge, Mass, assignor to Texas Instruments incorporated, Dallas, Tex., a corporation of Delaware Filed Aug. 23, 1961, Ser. No. 133,376 1 Claim. (Q1. 1113-44) This invention relates to the manufacture of snap-acting devices, and with regard to certain more specific features, to the manufacture of such devices having perforations therein.

Among the several objects of the invention may be noted the provision of a hydraulic method and apparatus for deforming and stressing perforated plate material, so

that it will thereafter function with snap action; and the provision of a method and apparatus of this class adapted for the manufacture of snap-acting devices of various shapes, both regular and irregular, including those with so called non-developable snap-acting deformed portions and of any of the monometallic, composite or bimetallic types. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, steps and sequence of steps, features of construction and manipulation, and arrangements of parts which will be exemplified in the constructions and methods hereinafter described, and the scope of which will be indicated in the following claim,

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

FIG. 1 is a side elevation of closed apparatus for carrying out the invention, parts being broken away;

FIG. 2 is a cross section taken on line 22 of FIG. 1; and

FIG. 3 is a fragmentary view showing certain parts of the apparatus in open position.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawmgs.

In the copending patent application of Charles D. Flanagan, Serial No. 133,506, filed August 3, 1961, eventuated as Patent 3,123,903, for Manufacture of Snap- Acting Devices is shown apparatus for forming, stabilizing and testing the snap-acting devices such as, for example, monometallic or bimetallic snap-acting plates of disc and other forms. For one form of the invention in said application, hydraulic fluid pressure is employed for the manufacture of unperforated snap-acting devices. For the manufacture of devices including those which may have perforations, a second method and apparatus are shown in said application which dispense with hydraulic pressurizing means. According to my invention, fluid pressurizing means may advantageously be employed for deforming perforated plates, so that they assume the desired snap-acting configuration. The advantages of utilizing fluid pressurizing forming means is more fully described in the aforesaid copending application. The plates contemplated herein may be monometallic, to constitute snap-acting spring devices, or composite, bimetallic or the like to form thermostatic devices. A bimetallic plate of perforated disc form is shown by way of example. The present method is also applicable to blanks which are partially preformed and also to those which have contacts or other attachments such as welding projections secured thereto prior to forming.

Referring now to the drawings, numeral 1 indicates a supporting framework for a pair of holders 3 and 5 for holding a disc 7 of bimetallic material of desired outline, which in the case of a disc is circular. Other outlines are also within the scope of the invention. The disc B,l53,l i Patented Dec. 29, 1964 is perforated, as shown at numeral 8, to provide ultimately for a central mounting post. The holders 3 and 5, when together as shown in FIG. 1, are intended to form a space divided into compartments 9 and 11 above and below the disc 7. The upper face of holder 3 is provided with a circular recess in which is an '0-ring 13. The lower face of the upper holder 5 is covered by a flexible resilient membrane or diaphragm 2, held in position by a marginal bead 4- therein snapped into a peripheral recess 6 adjacent the end of holder 5. Other fastening means may be employed, such as adhesive, vulcanization or the like. A suitable membrane or diaphragm material is a silicone rubber or polyurethane rubber.

Both compartments are flared, as shown at 10 and 12. The flare 12 includes a ledge 19, forming a narrow marginal support for a narrow margin of the disc 7. When the disc is in supporting position, it is preferable that its upper face be about flush with the upper face of the holder 3. Thus the upper surface of the disc is flatly engageable with the diaphragm 2.

Holder 5 is upwardly retractable from holder 3. This I is accomplished by a forked connection 21 on a piston rod 23, which may be driven up and down by means of a piston 25 in cylinder 27. Fluid control means 29 may be employed for operating piston 25. Numeral 31 indicates a stop threaded into the holder 3 and extending into the compartment 11, as shown. This preferably has a flat upper end. The desired amount of the projection of the flat end of the stop 31 into the compartment 11 is effected by turning it from a knurled head 35.

Compartment 3 is provided with a port 43 with which is connected a flexible pipe 51, leading from a source of hydraulic pressure which may be turned on and off. This pressure source includes a conventional stop valve, pressure-controlling reducing valve, release valve, pressure gage and the like. A breather port 45 connects compartment 11 with the atmosphere.

Operation is as follows, assuming the compartment 9 to have been infilled with a hydraulic fluid and line 51 connected:

The piston 25 is raised to retract holder 5 from holder 3. At this time, pressure is cut oil from line 51. A blank fiat or partially preformed disc is then placed on ledge 19. Stop 31 is adjusted so as to space its upper end from the disc a suitable amount for the deformation desired. Then the upper holder is lowered to squeeze the diaphragm 2 and also the O-ring 13 between it and the lower holder 3, the (2-ring 13 perfecting the seal. Then hydraulic pressure is applied from line 51 to compartment 9 of a sufficient value to deform the plate from the solid-line position shown in FIG. 1 to the dotted-line position on stop 31. If desired, application of pressure may be continued after contact between the center of the disc and stop 31, further to bulge the disc annularly around the disc. The diaphragm 2 seals the hole 8. Port 45 ac as a breather port for compartment 11.

As the plate is deformed into engagement at its mid portion with the stop, the plate becomes downwardly bulged and stressed in its bulged form, so that thereafter it becomes snap-acting in lmown manner. After the plate is thus formed, pressure is reduced in the compartment 9 and the holder 5 lifted for removal of the finished bulged snap-acting disc.

If desired, the disc may thereafter be inverted several times on its support 19 and the device reclosed upon each inversion for repeated application of pressures to reverse its curvature several times. By this means its internal stresses may be stabilized. Finally, in a position inverted in respect to that shown in FIG. 1, the pressure from line 51 may be slowly increased, noting the pressure required for snap action. This constitutes a step designed to test for the pressure at which snap action occurs after stabilization. Thus a disc may first be formed, then its stresses stabilized by several times reversing its curvature with snap action, tested for snap-acting characteristics. The testing step in effect determines the temperature at which the disc Will snap, because the pressure and ten1- perature at which it Will snap are correlated, provided the disc is of the bimetallic variety, as shown.

While the invention is particularly useful for making perforated snap-acting devices, it is also useful for making unperforated snap-acting devices.

An advantage of the present invention over the hydraulic method disclosed in the aforesaid copending application is that with the present apparatus and method, the fluid medium is retained in the compartment 9 after the forming of disc 7 takes place and compartments 9 and 11 are separated to permit removal of the formed disc. The pressure in compartment 9 is of course relieved prior to separation of the compartments. This advantageously minimizes the amount of fluid pumping required When the forming operation is to be repeated. By minimizing the fluid pumpage required, purging cycles are advantageously eliminated and faster operation and greater pressure control are afforded. The present method also 'rninimizes the likelihood of encountering entrapped gases.

It should be understood that, While the invention has been described as utilizing hydraulic pressure forming means, pneumatic means may also be employed in many situations.

It should be understood that it may also be desirable to provide a second diaphragm member on the opposite side of the disc whereby reverse forming and cycling for stabilization and testing of the disc may be performed with this apparatus by properly applying pressure to compartrnent 11 which is then sealed by the second diaphragm (not shown). Where the second diaphragm is employed it may be also desirable to employ a stop such as 31 in compartment 9. By isolating the disc form the forming pressure medium (i.e. fluid or gas) surface contamination of the disc is advantageously avoided thereby eliminating the necessity for subsequent costly and cumbersome cleaning operations.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

Apparatus for deforming perforated plates to form snap-acting members and for stabilizing and testing formed plates in the same apparatus; comprising a holder having a hollow portion formed with a margin for support of the edge portions of a plate to exteriorly expose either face thereof, a second hollow holder, a flexible diaphragm enclosing the hollow portion of said second holder, liquid filling in said hollow portion of the second holder held in place by said diaphragm, means for forcing said holders together to place the diaphragm adjacent the exposed face of a plate supported on said margin, peripheral sealing means surrounding the plate when the holders are forced together, means for applying and releasing pressure to and from said liquid When the holders are together to bulge the diaphragm and push an area of the plate into the hollow portion of the first holder to deform the plate within its margin, and a rigid central stop in the hollow portion of the first holder engageable only by a central portion of the plate when the plate is sutliciently deformed into the last-named hollow portion.

References ilted in the file of this patent UNITED STATES PATENTS 2,133,445 Guerin Oct. 18, 1938 2,375,599 Walton May 8, 1945 2,656,592 Cataldo et al Oct. 27, 1953 2,859,719 Kraybill Nov. 11, 1958 2,861,531 Moller Nov. 25, 1958 

